1. Field of the Invention
The present invention relates to a liquid-ejecting head that ejects a droplet of required liquid by generating an air bubble by the action of thermal energy on the liquid. The present invention also relates to a method of manufacturing such liquid-ejecting head, a liquid-ejecting apparatus, and a printing system using such liquid-ejecting apparatus as an output device.
2. Description of the Related Art
Heretofore, an ink-jet printing method, the so-called bubble-jet printing method, has been well-known in the generic public. The method comprises the steps of providing an ink with an energy such as a thermal energy to cause abrupt volume variation (generation of bubble) of the ink, and of ejecting the ink through ejection ports by an acting force on the basis of the state variation to deposit the ejected ink on a printing medium to form an image. The method has been used in: a printer as an output device of a data-processing apparatus such as a copy machine, a facsimile machine, an electronic typewriter, and a word processor; a printer as an output terminal of work station or the like; and a handy- or potable-printer of a personal computer, a host computer, an optical disk apparatus, a video apparatus, or the like. The ink-jet printing method is responsible for printing textual information and pictorial information on a printing medium by ejecting ink droplets on the printing medium, so that it has the excellent advantages of printing images with extraordinary definition and printing at high speed. In a liquid-ejecting head that employs the ink-jet printing method, ejection ports for ejecting the ink, ink passages communicating with the ejection ports, and electrothermal transducers as energy generating means for ejecting ink in the ink passages are typically arranged as disclosed in Japanese Patent Application Publication Nos. 61-59911 (1986) and 61-59914 (1986), U.S. Pat. No. 4,723,129, and the like.
The printing apparatus (hereinafter, also referred as the ink-jet printing apparatus) adopting the ink-jet printing method equips a removable or stationary liquid-ejecting head, and it shows the abilities of printing with a low noise level compared with that of the other apparatuses using the different printing methods because of: its non-impact printing system; printing a multicolor picture(both alphanumeric and graphic output in multiple colors) by using a set of different colored inks; and printing images with extraordinary definition at high speed. In recent years, therefore, the ink-jet printing method has been employed in a large number of office use apparatuses, such as printers, copy machines, facsimile machines and the like, and furthermore it becomes widely applicable to many industrial systems including a textile printing apparatus.
We are now explaining the method of manufacturing a liquid-ejecting head (hereinafter, also referred as an ink-jet printing head) in brief. In general, the ink-jet printing head is manufactured by the process including the steps of: separately preparing a flow-passage segment for the flow of ink and an ejecting-element segment; and fixing these segments together. To be more specific, for example, the following methods (I) and (II) have been known by the man skilled in the art.
(I) A first method (reference: The Journal of the Institute of Television Engineers of Japan, vol. 37, No. 2, 1983) comprises the steps of: forming a plurality of grooves as ink flow passages on a resin by a pressing technique using a die; forming layers of electrode, thermal resistance, over coat, and the like on a silicon base so as to be face to the grooves; and boding the resin and the silicon base together using a binder.
(II) A second method (reference: Japanese Patent Application Laying-open No. 2-16549 (1990)) comprises the steps of: performing an aeolotropic etching on a surface of a silicon substrate A using potassium hydroxide to form a plurality of grooves as ink flow passages; forming layers of electrode, thermal resistance, over coat, and the like on a silicon base B so as to be face to the grooves of the silicon substrate A; and bonding the silicon base substrates A and B together by anodize process.
One of the concrete examples of the ink-jet printing head manufactured by the above related art will be described below.
An ink-jet printing head in the type of side-shooter comprises: a base substrate on which thermal resistors and wiring conductors for applying current on that thermal resisters; and a top plate (nozzle-formed material) where a plurality of ink flow paths (i.e., nozzles) and their respective ejection orifices are formed.
In addition, there is a thermal resistance layer provided as a thermal resistor, on which an upper protective layer is formed for protecting the thermal resistance layer toward the ink and a lower protective layer is also formed on that layer for storing heart. To be more specific, this kind of the side-shooter type ink-jet printing head can be manufactured by the process comprising the steps:
patterning a plurality of ink flow paths and their respective ink-ejecting orifices by coating with nozzle-resist subsequently after forming a protective layer on both a thermal resistor provided on a Si-base plate and a wiring conductor for supplying electric-power to the thermal resistor; PA1 forming a through hole for supplying ink from the underside of the Si-base plate to the right side thereof after that the applied nozzle resist is hardened, and removing the nozzle resist through the hole to complete the above orifices to obtain a printing head board; PA1 cutting the obtained printing head board to the required length and then plating or forming a ball bump on a pad for TAB-bonding; PA1 bonding TAB to the obtained printing head for supplying electric-power from the outside source; PA1 dispensing a sealing resin on a region of the TAB-bonding for an electric insulation of TAB-bonded electric lead and for an improvement of strength of the TAB-bonding region (hereinafter, also referred as an exterior wiring portion); and PA1 hardening the resin in a furnace to obtain the ink-jet printing head. PA1 an ejection element portion having an energy-generating means for ejecting a liquid, a plurality of ejection orifices positioned in a direction perpendicular to the energy-generating means, and a wiring means for sending an electrical signal to the energy-generating means; PA1 an exterior wiring portion for applying the electric signal to the wiring means of the ejection element portion; PA1 an electrically connected portion where the wiring means and the exterior wiring portion are electrically connected together; and PA1 a sealing resin portion that seals the electrically connected portion, wherein PA1 a depression region is formed on the ejection element portion so as to be positioned between the plurality of orifices and one end portion of the sealing resin portion positioned between the plurality of orifices and the electrically connected portion, and PA1 the depression region limits a position of the one end portion of the sealing resin portion. PA1 forming a depression region on the ejection element portion so as to be positioned between the plurality of orifices and one end portion of the sealing resin portion positioned between the plurality of orifices and the electrically connected portion, wherein PA1 the depression region limits a position of the one end portion of the sealing resin portion. PA1 a carriage that moves along a main-scanning direction, on which a liquid-ejecting head for ejecting the liquid is removably mounted as a removable head or is fixed as a stationary head; PA1 a transporting means for transporting the printing medium; PA1 a control means for controlling movements of the liquid-ejecting head, the carriage, and the transporting means, wherein PA1 the liquid-ejecting head having: PA1 a control portion for processing an input information; and PA1 an output means for outputting a processed information from the control portion, wherein PA1 the output means is a liquid ejecting apparatus of claim 13.
For multicolor printing, three ink-jet printing heads are aligned in a row.
However, the ink-jet printing head described above has some problems to be solved as described in below with reference to FIG. 1A and FIG. 1B.
FIG. 1A is a diagrammatic plan view showing a the prime constituents of a liquid-ejecting head in accordance with the related art, and FIG. 1B is a cross sectional view along the line I-I' in FIG. 1A. In these figures, reference numeral 1 denotes a base plate having an ink inlet 12 opened from the underside to the right side thereof, on which an orifice plate 11 is formed so as to face to the ink inlet 12.
As shown in the figures, great attention should be given to the step of dispensing a sealing resin on an exterior wiring portion and its periphery so as to avoid that the sealing resin 21 is spread over the region including thermal resistor elements and ejection orifices 10. If it is not avoided, the sealing resin flows into a part of the orifice 10 or moves too closer to the orifice, causing ejection failure or degradation in ejection performance. This kind of problems should be solved especially when we design a smaller version of the liquid-ejecting head. The base plate size reduction is very important to respond to the demands of cost reduction for the lower prices of the liquid-ejecting head that result from market competition. The reason lies in the process of manufacturing the base plate as a thin film on which the ejecting element portion including thermal resistor elements and the like are formed. The thin-film processing technology permits a cost reduction by reducing the physical size of the base plate. However, the connected portion between the exterior wiring portion and the ejection element portion gets closer to the ejection orifices when the base plate is downsized. Therefore, the step of dispensing a sealing resin on the exterior wiring portion should be performed with a high degree of precision.
For solving the problems associated with the miniaturization of base plate, there is an idea of forming a projection on the ejection element portion to prevent a flow of the sealing resin flows into the orifices. However, the process of forming the projection has some problems. A first problem is that it requires a study of the height of the projection to be required to prevent the flow of sealing resin (i.e., approximately 0.1 mm). As a result, an additional step of forming the projection with high accuracy and an additional cost to prepare the material of protrusion or the like can be required. A second problem is that there is a possibility of preventing a movement of wiping means (such as a blade) by the protrusion and also there is a possibility of causing a wiping failure. The protrusion is formed on an end of the sealed resin region and a part of the blade comes into collision with the protrusion, so that an end portion of the blade is flipped as a result of its elastic property when the blade gets over the protrusion, resulting that the blade cannot wipe the ejection orifices in an appropriate manner. It is noted that there are another troubles to be occurred. For example, the wiping movement on an ink-ejecting surface of the head by means of blade along the nozzle arrangement can be prevented by the inappropriately dispensed sealing resin. Heretofore, accordingly, the condition of dispensed sealing resin is visually checked whether it is allowable or not. If it is not allowable (i.e., an abnormal sealed region is obtained), we judge the condition poor.
As described above, therefore, the process of manufacturing the liquid-ejecting head of the related art has some problems to be solved, including a cost up due to the visual check, reduced yields, and so on.